The objective of this study is to provide an ethnographic description and evaluation of an innovative social experiment, the Senior Block Information Service in San Francisco - a self-help effort at the grass-roots level aimed at a traditionally underserved population, the urban elderly. As the gerontological literature conclusively demonstrates, the urban elderly belong to very few voluntary associations or organizations, and participate only minimally even in those designed specifically for them. This research seeks to address the general problem of how social participation and involvement among the elderly can be increased, and isolation minimized, through the development of a new, emergent social form. Qualitative and quantitative data will be collected from members of the program staff, and from senior volunteers (approximately 425 in number), through participant-observation, and formal and informal interviewing, (1) to describe the full range of program activities; (2) to provide an assessment of the program's effectiveness in achieving its stated goals of reducing isolation and encouraging community involvement among, and providing information and referral services to, the aged; and (3) to lay the groundwork for a follow-up study aimed at evaluating the impact of such a community-based service program on perceptions and behavior of the elderly who participate in it. On the basis of the data generated in the study, patterns should emerge which will suggest hypotheses and questions for further study, and for generating a model suggesting which conditions and factors may be most relevant in defining or determining the optimal level of senior participation in voluntary associations and in self-help outreach efforts designed for the elderly. The research should, be of theoretical and practical interest to planners and policy-makers who design and implement programs for the aged, particularly in the area of preventive mental health; to gerontologists and social scientists in general; and to the elderly themselves.